The present invention relates to a door driver and more particularly to a door driver which moves a railway house car door between a locking position and a sliding position.
When a railway car is in use, cargo is loaded into the railway car by opening the railway car door and moving the cargo to be transported into the car either manually or by mechanical means, such as a lift truck. Once the cargo is loaded into the railway car, the railway car door is closed and locked in that position. When the railway car reaches its destination, the railway car door is unlocked and opened and the cargo is removed from the railway car. In some cases, the cargo is palletized and must necessarily be handled by lift trucks to reduce the labor for loading and unloading operations, considerable damage has been caused to doors and the railway car side parts adjacent to the doorway. For example, the lift hooks of the lift trucks have inadvertently caused such damage by hitting the front stops on the car frame and the front edges of the sliding railway car door. After such damage has been caused, it is extremely difficult to open or close the door manually since there is extreme binding between the front stops on the railway car and the front edges of the railway car door. In the field, a lift truck has been used to move the door into a locking position by exerting substantial force on the door. This operation in turn causes additional damage.
In order to alleviate this problem various modifications to the door engaging members, both on the door and the structural frame of the railway car, have been made. One such modification is moving the door engaging member away from the door opening so that the lift trucks and their pallets do not hit these members. These solutions have reduced the frequency of damage but have not completely eliminated the problem so that it still exists at a lesser frequency.
Present door locking mechanisms have starters and closers that move the door out of or into the lock position over a small distance. One such prior art mechanism is disclosed in Madland, U.S. Pat. No. 3,279,839. Madland discloses a lever which is capable of exerting a force on the railway car door which urges the railway car door towards a locking position. This design develops a minimum mechanical advantage under optimum conditions. In most cases of deformation of car side parts or doors, this mechanical advantage is insufficient to overcome the binding forces with a force manually applied to the lever. Thus, the use of a lift truck or a come-long device is required.
As is apparent from the above, the primary reason for using a door driver is to exert a force to move the door into and out of a locking position which force is sufficient to overcome binding forces between the railway car body or frame and the door. It is particularly desirable that this force is exerted by manual means and not by the use of any auxiliary equipment which is expensive, time consuming and if not properly designed may create additional damage to the door or railway car frame. It is also desirable that the door driver be capable of moving the railway car door a substantial distance under such greater force. When a lock mechanism is utilized, it is also desirable to provide a door driver which is capable of slightly moving the door when it is in the lock position so that the lock may be easily released.